Tree Fruit IPM Report for April 11, 2023

Tree Fruit Phenology: Tree Fruit Phenology remains advanced in peach, but development is slowing. In southern counties all peach orchards are late bloom to petal fall. Redhaven was at approximately full bloom on April 4. Plums are at shuck off. Pears are at petal fall. Red Delicious is just past full bloom. Sweet cherries are at late bloom depending on variety.

Peach:

Brown Rot: Blossom infections from the brown rot fungus can occur whenever pistils are exposed and a favorable climate exists. Infections can occur during any wetting period when temperatures are between 41 and 86 °F. However, optimum conditions for infection occur with wetting and temperatures in the mid 70’s. During long wetting periods (several days or more) blossoms can be infected regardless of temperature. Generally infections that occur when conditions are sub optimal are less severe. Blossoms and fruitlets will remain susceptible until the pistil dessicates (sometime between petal fall and shuck split). Initiate coverage for blossom blight starting at pink for short petaled varieties and 5-10% bloom for showy flowers. See the NJ Commercial Tree Fruit Production Guide for recommended materials and rates.

Bacterial Spot: Copper formulations should be used starting at petal fall to suppress bacterial spot. Generally we recommend starting at 0.5 ozs metallic copper and gradually lowering the rate as the season progresses. The rate applied will depend on the formulation. Dr. Lalancette published a chart listing common copper formulations and rates for peach and nectarine applications. Avoid combining copper with captan especially if it has been overcast for several days. Also avoid acidic spray solutions when applying copper. Dr. Lalancette has published a handy guide for copper applications in early covers. Antibiotics such as Mycoshield or Fireline may also be used and may offer slightly more residual activity during long wetting periods.

Peach Scab: In addition to Rusty Spot and Bacterial Spot, Peach Scab requires protective applications starting at petal fall. Peach scab cankers (Fig. 2) begin to expand at bloom and by shuck split begin to shed spores during wetting periods. Topsin, Topsin/Captan combinations, Flint Extra, Inspire Super, and especially Quadris Top applied at petal fall are the best materials for blocks that had scab last year. Quadris Top, Flint Extra or Topsin should be used at the high rate to suppress overwintering lesions on the wood. Quadris Top contains azoxystrobin which is phytotoxic to many apple varieties. Phytotoxic residues can remain in the tank for long periods after an application is made, even if a tank cleaner is used. Do not use Quadris Top or Abound in the same sprayer used for apples. Bravo (chlorothalonil) is also a good protectant that may be applied no later than shuck split. Captan is also helpful in cover sprays after shuck split where scab was troublesome last year.

Fig. 2 Peach Scab lesions on peach twig.

Oriental Fruit Moth: A biofix point for OFM was set on 4/10 in both northern and southern counties. No biofix has been set for northern counties. The first insecticides for first generation Oriental Fruit Moth control should be applied at 170-200 degree days base 45 after biofix. This timing generally coincides with 100% petal fall in peaches.  Do not apply insecticides until all bloom is off. No Insecticides for OFM are needed where Mating Disruption is implemented.

Green Peach Aphid: GPA colonies begin forming sometime during bloom. Examine trees for the presence of colonies from pink to shuck split. Count the number of colonies on ten trees and use a treatment threshold of 2 colonies/tree at petal fall for peach, and 1 colony/tree for nectarine. The best way to scout for aphids during bloom is with a beating tray. Blossoms may also be collected, opened, and examined for the presence of aphids using a hand lens. This is particularly important for nectarine blocks. Check 10 trees per block with the beating tray. Collect 50 blossoms per block and examine for the presence of aphids. If more than 1 colony of aphids are found in nectarines, or 2-3 colonies are found in peaches, an insecticide for aphids will be needed when all petals are off. See the NJ Commercial Tree Fruit Production Guide for recommended materials and rates. No aphid activity has been noted on southern counties to date.

Plum Curculio; Tarnished Plant Bugs; and Other Catfacing Insects: Plum Curculio start to move into orchards at about 88-100 degree days base 50 after January 1. Applications for PC should be initiated once all petals are off, with a second application made with ovicidal materials at 379-402 DD. Currently we have accumulated about 100 DD base 50 in southern counties. Growers can monitor degree day development at their site by finding the nearest weather station and using the degree day development tool at NEWA. Catfacing insects are starting activity but cause little damage at this time of the year. Catfacing insects will become more of an issue as temperatures warm and mowing and other ground cover activities become more common after bloom. Insecticides for catfacing insects are not recommended until after all petals are off.

Scale Insects: Dormant oil applications are standard recommendations for scale control, but in some years conditions are not good for oil and control is less than desired. Where scale has been recurring the application of Movento at petal fall to shuck split has “cleaned up” chronic scale outbreaks. Movento should be applied at 6-9 ozs/ac. a penetrant must be included as described on the product label. Movento will also control green peach aphid at this timing.

Apples and Pears:

Diseases: Fire Blight, Apple Scab, Rust diseases, and Powdery Mildew are the main targets at this stage. The NEWA apple scab model is estimating about 27% ascospore maturity as of 4/10 in southern NJ with ony 6 % of cumulative ascospores discharged. Northern counties were at Green tip on or about 4/3. The model estimates about 5% ascopsore maturity for Northern Counties with only 1% ascopres released. Primary apple scab spores are released during any substantial infection period. More information can be found in this blogpost from Penn State. Between tight cluster and first cover include products effective  for powdery mildew and cedar apple rust. To manage Fire Blight in both apples and pears, consider using Kasumin at bloom. Kasumin is an antibiotic like Streptomycin and Oxytetratracycline. It contains Kasugamycin which is a different chemistry. Kasumin is only labeled for bloom and petal fall applications while strep and oxytet are labeled for post bloom use. Using 3 different chemistries in rotation allows for resistance management while extending the protection into the post bloom period when late blossoms typically appear which ever material you use, the addition of Actigard or other plant defense elicitors may improve control.

Rust Diseases: The two most common rust diseases that affect pome fruit are Quince Rust and Cedar Apple Rust. In some years these diseases can be troublesome in commercial orchards. Most disease control programs for scab will also control rust. In organically managed blocks in the east options are limited for approved materials that are effective for rust. Potassium Bicarbonate products have shown good efficacy for rust diseases in trials performed in Virginia. Organic growers should seek out and plant rust resistant cultivars. Cultural controls are not practicable due to the widespread presence of alternate host Junipers both wild and cultivated. Rust disease development on junipers should now be producing large spore releases during wetting periods. See this link for pictures of rust on pome fruit and juniper.

Scale Insects: Dormant oil applications are standard recommendations for scale control, but in some years conditions are not good for oil and control is less than desired. Where scale has been recurring the application of Movento at petal fall to shuck split has “cleaned up” chronic scale outbreaks. Movento should be applied at 6-9 ozs/ac. a penetrant must be included as described on the product label. Movento will also control green peach aphid at this timing.

Rosy Apple Aphid:  If a pre-bloom application was not made, monitor for colonies during bloom and use a treatment threshold of 1 colony/tree at petal fall.

Pear Psylla:  Dormant oil applications should have already been started to deter psylla egg laying. At the green cluster stage a pyrethroid or Esteem is generally included with oil. Pyrethroids may knck down some of the adults migrating into the orchard, while Esteem may sterilize them.  In lieu of oil or insecticides, Surround may also be applied starting at swollen bud and continued through petal fall. If using Surround through the bloom period stop at petal fall and switch to applications of 1% summer oil @ 1gal/ac in no less than 150 gals/ac. these should be made at no more than 2 week intervals. At petal fall insecticide options for Psylla control include Actara, Assail, Belay, Movento, Sivanto Prime, and Agri-mek. See the NJ Commercial Tree Fruit Production Guide for recommended materials and rates.

Pear Diseases:  Include effective materials such as Ziram or EBDC formulations for Pear Scab and Rust diseases beginning at the cluster bud stage. At white bud use products effective for pear scab, rusts, and fabrea leaf spot. For both apples and pears, consider using Kasumin at bloom. Kasumin is an antibiotic like Streptomycin and Oxytetratracycline. It contains Kasugamycin which is a different chemistry. Kasumin is only labeled for bloom and petal fall applications while strep and oxytet are labeled for post bloom use. Using 3 different chemistries in rotation allows for resistance management while extending the protection into the post bloom period when late blossoms typically appear. which ever material you use, the addition of Actigard or other plant defense elicitors may improve control.

Grapes: Grapes are at budbreak to the 1″ stage of development. The most important disease to manage at this time is Phomopsis. Insect pests to monitor are Grape Flea Beetle, and Climbing Cutworms. Controls for these insects are rarely needed. If control is determined to be necessary, use one of the materials recommended in the New Jersey Commercial Grape Production Guide. Remember that Lorsban has lost all food tolerances and should not be used. It’s also not too late to scout for and destroy SLF egg masses on posts and trunks.